• Microsoft is replacing OpenAI and Anthropic models with its own MAI models in parts of Excel and Outlook, handling tens of thousands of prompts weekly.
  • The company maintains a multi-model strategy, using a mix of MAI, OpenAI, and other sources to optimize performance, cost, and control.
  • This move reduces supplier risk and aligns with broader industry trends toward diversified AI sourcing.

In-House AI Takes Over Productivity Apps

Microsoft has begun substituting OpenAI and Anthropic's AI models with its own MAI models in select features of Excel and Outlook, according to people familiar with the matter. The Redmond-based tech giant is now routing tens of thousands of prompts each week through its internally developed models, signaling a pivot toward self-reliance in AI capabilities.

The shift is not an outright replacement, however. Microsoft continues to rely on OpenAI for frontier models and other external providers when advantageous. "We are expanding our options," a company spokesperson said, emphasizing that collaboration with OpenAI remains intact.

A Multi-Model Approach

Industry observers note that Microsoft's strategy mirrors a broader trend among big tech firms to develop proprietary AI while hedging against over-dependence on a single supplier. By balancing MAI, OpenAI, and third-party models, Microsoft can tailor performance, cost, and governance for each task.

In practice, this means some Outlook features that previously used OpenAI's GPT models now run on MAI, while other apps like Word and Teams may still rely on external models. The company declined to specify which features have been migrated, citing competitive sensitivity.

Implications for Competitors and Clients

For enterprise customers, the shift could bring tighter integration with Microsoft's ecosystem and potentially lower costs if MAI models prove cheaper per prompt. However, privacy advocates may welcome the move, as in-house models allow more direct control over data handling.

Competitors like Google and Amazon are expected to accelerate their own internal model development, while startups such as Anthropic may face reduced reliance from one of their largest customers.

Correction: An earlier version of this article stated that Microsoft had fully replaced OpenAI models. In fact, the company maintains a multi-model strategy and continues to use OpenAI for certain applications.